#阶乘   5
#1*2*3*4*5 = 120
def getNum(n):
    sum = 1
    i = 1
    while i <=n:
        sum *= i
        i += 1
    return sum
i = int(input("请输入想要求的阶乘数字: \n"))
num = getNum(i)
print(num)